1. Field
Example embodiments relate to a memory system, and more particularly, to a semiconductor device that screens a weak bit from among memory cells and repairs the weak bit, and a memory module and a memory system which include the semiconductor device.
2. Related Art
A semiconductor device that is widely used in a high-performance electronic system has increased capacity and speed. A dynamic random access memory (DRAM), which is an example of the semiconductor device, may have a decreased cell capacitor and a small feature size according to a process scaling. However, due to the decreased cell capacitor and the small feature size, various device characteristics may deteriorate. For example, cells having a short refresh time may increase in number, a cell write characteristic may deteriorate, or cells having a variable retention time may increase in number. However, an area penalty problem of a DRAM chip may be caused when the weak cells with the aforementioned weak characteristics are replaced by using redundancy DRAM cells.